462 
Ridley .— Symbiosis of Ants and Plants . 
This, however, could not be classed as symbiosis, but rather as a modi¬ 
fication for fertilization, as the main nest of the ants is apparently always 
underground near the tree. 
Dischidia Rafflesiana, Wall. 
This remarkable plant, so common in the southern part of the Malay 
Peninsula, has been a subject of a very considerable amount of literature, and 
has been classed by Beccari and others as a myrmecophilous plant. 
It is plentiful in the Botanic Gardens at Singapore, and there is an old 
Durian tree preserved for its cultivation which is almost covered with this 
plant. This tree also bears Pleopeltis sinuosa and Drymoglossnm piloselloides 
in abundance. 
This Dischidia is one of the Asclepiadeae, a climbing epiphyte, which 
bears two forms of leaves, one round and fleshy, and one cone-shaped, with 
an opening at the base (the broadest part), and an inverted rim inside the 
opening. Through this opening the roots project into the hollow cone. 
The cone-shaped or rather pitcher-shaped leaves are green, or more usually 
yellow outside and purple within, and are generally arranged in pairs or fours 
in an irregular false whorl or cluster. 
The sole advantage to the plant obtained by the presence of ants 
in the pitchers could be but the supplying of food in the form of the nest- 
d^bris to the roots enclosed in the pitcher ; much after the same way 
as Platycerium is supplied with food by the ants. No insects, so far as we 
know, attack the plant or are likely to, so that the Dischidia would gain 
nothing by inducing the ants to come as guards. The advantage mentioned 
is undoubtedly a valuable one to D. Rafflesiana , but it must be pointed out 
that the tenancy of the pitchers by ants is not constant, nor even very 
common, and there does not seem to be any material superiority of plants 
tenanted over those which are not tenanted. In the case where there is an 
ants’ nest in the pitcher, the roots seem to be somewhat more extensively 
developed, and they are soon found in contact with the detritus. All the 
pitchered Dischidia that I have met with, viz. D. Rafflesiana and D. com¬ 
plex ■, grow in very hot exposed positions on thinly foliaged trees, positions 
where the roots are exposed to an excessively hot sun. The plants scramble 
over and twine round the branches, and the roots could not be protected 
from drought as they are in D. collyris , Wall., in which the convex leaves are 
closely appressed to a tree trunk, with their margins touching and so 
covering completely the roots. The only position in such an exposed place 
as that usually inhabited by D. Rafflesiana where the roots could develop 
sufficiently for absorptive purposes, is in the hollow of the pitcher where the 
water-vapour can be absorbed. From the inverted saucer-shaped leaves of 
D. collyris to the pitchers of D. Rafflesiana is a comparatively simple develop¬ 
ment. Beneath the leaves of D. collyris and the somewhat similar ones of 
